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63 lines
1.7 KiB
63 lines
1.7 KiB
13 years ago
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/*
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* Copyright 2012 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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class Sin {
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public:
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Sin();
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static void init();
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static int32_t lookup(int32_t phase);
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static int32_t compute(int32_t phase);
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// A more accurate sine, both input and output Q30
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static int32_t compute10(int32_t phase);
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};
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#define SIN_LG_N_SAMPLES 10
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#define SIN_N_SAMPLES (1 << SIN_LG_N_SAMPLES)
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#define SIN_INLINE
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// Use twice as much RAM for the LUT but avoid a little computation
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#define SIN_DELTA
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#ifdef SIN_DELTA
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extern int32_t sintab[SIN_N_SAMPLES << 1];
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#else
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extern int32_t sintab[SIN_N_SAMPLES + 1];
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#endif
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#ifdef SIN_INLINE
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inline
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int32_t Sin::lookup(int32_t phase) {
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const int SHIFT = 24 - SIN_LG_N_SAMPLES;
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int lowbits = phase & ((1 << SHIFT) - 1);
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#ifdef SIN_DELTA
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int phase_int = (phase >> (SHIFT - 1)) & ((SIN_N_SAMPLES - 1) << 1);
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int dy = sintab[phase_int];
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int y0 = sintab[phase_int + 1];
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return y0 + (((int64_t)dy * (int64_t)lowbits) >> SHIFT);
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#else
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int phase_int = (phase >> SHIFT) & (SIN_N_SAMPLES - 1);
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int y0 = sintab[phase_int];
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int y1 = sintab[phase_int + 1];
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return y0 + (((int64_t)(y1 - y0) * (int64_t)lowbits) >> SHIFT);
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#endif
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}
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#endif
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